Fungal metabolites of the epidithiodiketopiperazine class exhibit antitumor and antiviral activity. The members of this class--gliotoxin, aranotin, chaetocin, verticillins, sporidesmins, etc.--can be divided into two classes dependent on whether they are derived biogenetically from phenylalanine or tryptophan. The apparent biogenetic pathway from phenylalanine is via intermediate arene mono- and diepoxides. Syntheses of these substances utilizing such key intermediates are being explored. On the other hand the key step in the biogenesis of chaetocin and the venticillins appears to be a tyrptophan dimerization. Such dimerizations have been realized in the laboratory with model tyrptophan derivatives and this approach is being examined for the total synthesis of chaetocin and the verticillins.